The present invention relates to the diagnostic imaging arts. It finds particular application in conjunction with the real-time display of medical diagnostic images and will be described with particular reference thereto. However, it is to be appreciated that the invention may find application in conjunction with non-medical imaging, volumetric imaging, and the like.
Heretofore, x-rays have been projected through a patient onto a flat film box on the other side of the patient. X-ray film mounted in the film box was exposed with a projection of the radiation opacity of the tissue or other internal structure of an examined subject. Because all of the internal structure was projected into a common plane, such images were difficult to read.
Conventional x-ray tomo systems have a similar construction, but include structure for moving the x-ray tube and the film box counter-cyclically in planes parallel to the x-ray film. More specifically, a center ray of the x-ray beam was projected through the region of interest to the detector. The x-ray source and the detector were then moved such that the central ray pivots about a fixed point in the plane of interest. With this process, not only does the central ray pivot about the plane or slice of interest, the other rays from the x-ray source to the film box do as well. In this manner, the x-ray attenuation contribution to the final image from volumetric elements within the selected plane remains constant during the imaging procedure. However, outside of the selected slice, each of the rays pass through different surrounding tissue or structures as the source and detector move. In this manner, the contributions to the final image from structures outside of the plane of interest become blurred and averaged. With a sufficiently long exposure and motion through a relatively wide range, the out-of-slice structures can be reduced to background noise while the in-slice structures are displayed crisp and clear. Such systems required a significant time lag before the diagnostic image could be viewed. First, there was a delay while the x-ray source and the film box and the film box were moved back and forth to expose the film. This was followed by a further delay as the film was developed.
Real-time images were available from fluoroscopy systems. In a fluoroscopy system, the x-rays are projected through the patient onto an image intensifier, i.e., a fluorescent screen and electronics to make the resultant image brighter. A video camera was mounted to view the image generated by the image intensifier. The video camera was connected by a closed-circuit TV system with a monitor for viewing the fluoroscopic images. Although these images were real-time, they were again projection images which superimposed all the structure in the field-of-view onto a common plane. Moreover, image intensifiers were subject to non-uniform brightness across the field-of-view and significant image distortions. Fluoroscopic images typically had much less resolution than projection x-ray.
CT scanners have been utilized to generate images of internal structures quickly. However, CT scanners typically view the patient in slices which are orthogonal to those of the tomographic x-ray systems. That is, with the patient positioned prone on his back in the scanner, the tomographic x-ray systems generated an image of a horizontal slice. With the same orientation of the patient, CT scanners generate a vertical slice. Of course, CT scanners can be utilized to generate a large multiplicity of slices to define a volume from which a horizontal slice can be extracted. However, taking a large number of slices again introduces a time delay. Moreover, CT scanners are expensive and capable of performing only a limited number of diagnostic tasks.
The present invention contemplates a new and improved imaging technique which overcomes the above-referenced problems and others.